I like keeping all my history in one place, so there is a postscript to my tale.
After Jack sent me the email telling me that our relationship was over, I was puzzled, since the last time I had talked to him, the day before, we were flirting a little and talking about going hot-tubbing together. So I wrote to him and asked what had gone amiss. I expected that Cait had just put her foot down once and for all about me. By the time I got a reply from him, I didn't have the heart to read it. I just forwarded it to Jared and asked him to tell me the gist of it. He said that Jack said that he had decided to end our relationship because I had written to him, the day before, that Cait was still angry and resentful and that made me sad. Since she'd been shouting at me in the middle of a restaurant on and off for three hours straight, not three days prior, I thought my observation was pretty much spot on, but Jack took what I said as unfair criticism of her. At that point, I decided it was time to step away from the crazy and I did not reply to him at all. I did not block him from contacting me though. He tried to get in touch with me via IM less than a week later. I was too upset to talk to him, so Jared interceded and told him I just wasn't ready to be in touch with him yet.
While I already knew I did not want Jack as any kind of platonic friend or IM buddy, I figured that eventually he and I would settle down to be civil and polite in public places, if nothing else.
Jared was not satisfied with what he knew about what had happened. It didn't add up for him, that Jack had discussed getting together with me and then dumped me barely 12 hours later. Cait was still writing to Jared, mostly hostile emails trying to get him to concede that everything that had happened was 100 percent my fault, and she had no responsibility for anything that had happened. For some reason, even though she was a condescending bitch to him in her emails, and even though he'd caught her in a pretty outrageous lie, she still seemed to want him to have a good opinion of her.
I urged him to block Cait if she was upsetting him, but he wanted some answers, so he asked her a few questions. She said that Jack had been writing a breakup email to me while he was making plans to go hot-tubbing with me, that he had no intention of following through on those plans, and she made it sound like they were actually laughing at me while he and I were IMing. Also, that he took my interest in hot-tubbing with him as soliciting sex from him, even though I had explicitly said that sexual activity was not permitted at the venue and one could actually be banned from the place for violating that rule. I was nowhere near ready to be intimate with him, and I thought I made that clear to him, but he preferred to think otherwise (his ego was way bigger than another part of him, apparently), and led Cait to believe that too.
Jared could not believe that Jack had really toyed with me like that, so he wrote to him and asked if it was true. He said that Jack didn't deny any of it.
At that point, I blocked Jack from being able to contact me online in any way, shape, or form, and even blocked his phone number. Cait was already blocked. Jared hasn't blocked them yet, but I think he's pretty close to that point, since Cait is still sending him poison pen emails, two months later, squawking that he has no right to blame her for what happened. Some people just can't let go, I guess.
I don't quite understand how I fell in love with someone so vile. I feel like an idiot. But it's made it easy to get over him. I don't miss him or any aspect of our relationship now. I'm just glad it's over. I am hoping that Jared and I don't trip over them in this very small poly world of ours, but if we do, we will just ignore them both.